1. Field of the Invention
The present invention relates to a photovoltaic device including a crystalline semiconductor substrate of first conductive type having a first main surface and a second main surface, and a semiconductor layer of second conductive type formed on the first main surface of the crystalline semiconductor substrate, and relates to a manufacturing method of the photovoltaic device.
2. Description of the Related Art
There is a growing demand for photovoltaic devices in various sizes to meet the needs of consumers in recent years. As a method of manufacturing photovoltaic devices in various sizes, there is a method where photovoltaic devices are formed by use of a substrate in a standard size and then are separated into a desired size.
For example, Japanese Unexamined Patent Publication No. 2001-274441 discloses a method of separating a glass substrate into photovoltaic device. According to the method, photovoltaic devices made of a glass substrate formed by transparent electrodes, amorphous silicon films, and metal electrodes thereon are subjected to irradiation of a laser beam. The laser beam is irradiated onto positions to be separated, from the metal electrode side. Thus, trenches are formed at the positions from which the metal electrodes, the amorphous silicon films, and the transparent electrodes are removed. And then, the glass substrate is cut along the trenches into the photovoltaic devices of a desired size.
Meanwhile, studies and practical applications of solar batteries serving as photovoltaic devices, which are made of crystalline silicon such as single-crystal silicon or polycrystalline silicon have been actively pursued in recent years. Among them, a solar battery having a heterojunction that is formed by combining an amorphous silicon and a crystalline silicon attracts much attention due to its capabilities to obtain the heterojunction in a low-temperature process equal to or below 200° C. and to obtain high conversion efficiency.
FIG. 1 is a schematic cross-sectional view for explaining an example of such a solar battery having a heterojunction that is formed by combining an amorphous silicon and a crystalline silicon. A solar battery 50 has a structure in which an intrinsic amorphous semiconductor layer 3, a p-type amorphous semiconductor layer 4, a p-side transparent conductive film layer 5, and a p-side collector electrode 6 are formed on one main surface of an n-type crystalline semiconductor substrate 2 in the stated order. Moreover, an intrinsic amorphous semiconductor layer 7, an n-type amorphous semiconductor layer 8, an n-side transparent conductive film layer 9, and an n-side collector electrode 10 are formed on the other main surface of the n-type crystalline semiconductor substrate 2 in the stated order.
As described above, in the case of manufacturing the photovoltaic devices in the desired size having a heterojunction formed by combining an amorphous silicon and a crystalline silicon, the process is firstly to form trenches at the portion where the separation process will be performed by removing the collector electrodes, the amorphous semiconductor layers and the intrinsic amorphous semiconductor layers, and then to separate the photovoltaic devices along the trenches. However, the process according to above described disclosure may lead to reductions in the open voltage Voc and the fill factor F. F. from time to time.